The present disclosure relates generally to systems and methods for communications between a wireless device or user agent (UA) and a network and, more particularly, to systems and methods for coordinating communications resources between wireless devices and networks including circuit switched networks.
As used herein, the term “user agent” or UA can refer to wireless devices such as mobile telephones, personal digital assistants (PDAs), handheld or laptop computers, and similar devices, including mobile stations (MS) or user equipment (UE) that have telecommunications capabilities. In some embodiments, a UA may refer to a mobile, wireless device. The term “UA” may also refer to devices that have similar capabilities but that are not generally transportable, such as desktop computers, set-top boxes, or network nodes.
A UA may operate in a wireless communication network that provides high-speed data and/or voice communications. The wireless communication networks may implement circuit-switched (CS) and/or packet-switched (PS) communication protocols to provide various services. For example, the UA may operate in accordance with one or more of an Enhanced Universal Terrestrial Radio Access Network (E-UTRAN), Universal Terrestrial Radio Access Network (UTRAN), Global System for Mobile Communications (GSM) network, Evolution-Data Optimized (EV-DO), Digital Enhanced Cordless Telecommunications (DECT), Digital AMPS (IS-136/TDMA), Integrated Digital Enhanced Network (iDEN), Universal Mobile Telecommunications System (UMTS), Enhanced Data rates for GSM Evolution (EDGE), GPRS/EDGE Radio Access Network (GERAN) and General Packet Radio Service (GPRS) technology. Other wireless networks that UAs may operate in include but are not limited to Code Division Multiple Access (CDMA), cdma2000, cdma2000 1xRTT, cdma2000 HRPD, WLAN (e.g. IEEE 802.11) and WRAN (e.g. IEEE 802.22). UAs may also operate in fixed network environments such as, for example, Digital Subscriber Line (xDSL) environments, Data Over Cable Service Interface Specification (DOCSIS) cable networks, Wireless Personal Area Networks (PAN), Bluetooth, ZigBee, Wireless Metropolitan Area Networks (MAN) (e.g., WiMAX, IEEE 802.20, IEEE 802.22 Ethernet) or optical networks. Some UAs may be capable of multimode operation where they can operate on more than one access network technology either on a single access network at a time or in some devices using multiple access technologies simultaneously.
In wireless telecommunications systems, transmission equipment in a base station transmits signals throughout a geographical region known as a cell. As technology has evolved, more advanced equipment has been introduced that can provide services that were not possible previously. This advanced equipment might include, for example, an evolved universal terrestrial radio access network (E-UTRAN) Node B (eNB) rather than a base station or other systems and devices that are more highly evolved than the equivalent equipment in a traditional wireless telecommunications system. Such advanced or next generation equipment may be referred to herein as long-term evolution (LTE) equipment, and a packet-based network that uses such equipment can be referred to as an evolved packet system (EPS). As used herein, the term “access device” will refer to any component, such as a traditional base station, eNB, or other LTE access device, that can provide a UA with access to other components in a telecommunications system.
The different networks described above provide varying services to connected UAs. Some networks, for example, provide only PS services and cannot provide CS voice or other CS domain services. As such, a UA may be configured to connect to multiple network-types to access both PS and CS domain services. For example, if a UA is connected to a first network cell that does not provide CS domain services, the UA may be configured to implement a CS fallback procedure, which may be referred to herein as “CS fallback”, to connect to an accessible network such as a GERAN or Universal Terrestrial Radio Access Network (UTRAN) to access the voice or other CS domain services provided by those networks. As such, the CS fallback procedure allows a UA connected to a network using a first radio access technology (RAT) and that provides only PS domain services, to connect to another network that provides CS domain services. CS fallback may be used, for example, to initiate voice calls via a cell of a network providing CS domain services, when, at the time of initiating the voice call, the UA was associated to a cell of a network that only provides PS domain services. The UA initiating the voice call may be either idle or connected (e.g., active) on the cell of the network that only provides PS domain services. In case the UA is idle, it can be said to be camped on the cell and may be monitoring the paging channel of that cell for paging messages for mobile terminated sessions or calls. In case the UA is connected, it may be communicating with the cell and transferring data for a PS domain service.
Turning to FIG. 1, an example CS fallback process is illustrated whereby a UA 10 transitions from an E-UTRAN network cell 12 to a GERAN or UTRAN cell 14 to access CS domain services for initiating a voice call. As will be described, to facilitate CS fallback, the UA 10 may be configured to communicate with both PS-based and CS-based networks. For example, the UA 10 may support combined procedures for EPS/International Mobile Subscriber Identity (IMSI) attach, and Tracking Area update for registering with a Mobility Management Entity (MME) to access PS domain services (for example, via an E-UTRAN, UTRAN or GERAN access network) and for registering with a Mobile Switching Center (MSC) to access CS domain services (for example, via a UTRAN or GERAN access network or another network supporting CS domain services). The combined procedures also allow the MSC and MME to create an association between one another so that each is aware that the UA 10 is simultaneously registered with both the MSC and MME and that, therefore, the UA 10 is registered with both the PS and CS network.
FIG. 2 is a data flow diagram illustrating an example data flow for a mobile-terminated CS fallback procedure where the UA 10 in connected mode is redirected to GERAN or UTRAN. In FIG. 1, the UA 10 is initially connected to E-UTRAN cell 12. Because E-UTRAN cell 12 does not provide CS domain services, UA 10 implements CS fallback to communicate with the GERAN or UTRAN cell 14 to access CS domain services provided thereby.
By way of example, a network assisted cell change (NACC) related to a mobile originated voice call will be described. Referring to FIGS. 1 and 2, the example process begins by a MSC 16 sending a CS paging 18 to a MME 20, which in turn prompts the MME 20 to send a CS service notification paging 22 to the UA 10. In FIG. 1 communications from the E-UTRAN cell 12 are indicated by arrow 23 and communications from the UA 10 to the E-UTRAN cell 12 are indicated by arrow 25. Responsive to the CS service notification paging 22, the UA 10 sends an Extended service request 24 to the eNB 26 of the E-UTRAN cell 12. However, the E-UTRAN cell is not configured to provide CS domain services. Thus, the MME 20 sends a S1 application protocol (S1-AP) message with a CS fallback indicator 30 to the eNB 26.
To streamline the exemplary data flow, FIG. 2 indicates some data flows by boxes, such as optional measurement report 32 which may be provided by the UA 10 to indicate information, such as signal strength and the like of neighboring cells to which it may be assigned. That is, when performing CS fallback, the UA 10 may be in the best position to determine which cell or cells are candidate cells to which to fallback. As such, the UA 10 can detect which cells are in close proximity or have particularly strong received signal strength or quality (or other such parameters), and hence with which cells the UA 10 would likely have a successful connection following the CS fallback process. Accordingly, during the CS fallback process, the UA 10 may undertake a measurement step to detect and identify the cells accessible to the UA 10. In other words, before falling back to a cell providing CS domain services, the UA 10 may search for available candidate network cells via a measurement process.
The eNodeB (eNB) may trigger an inter-RAT cell change order, optionally with NACC signal 34 that is sent to the UA 10, alternatively a connection release with redirection is signaled 36. The eNB 26 indicates, according to S1-AP, a UA context release request 38 to the MME 20. Thereafter, the S1 UA context release 40 takes place, a location area (LA) update, a combined routing area (RA)/LA update, a RA update, or a LA update and RA update 42 occurs in the new GERAN or UTRAN cell. If the target RAT is GERAN, a suspension of PS services may take place if the new cell or the UA does not support concurrent CS and PS services. In this case, a suspend message 44 is sent from the UA 10 to a base station system (BSS) 46, which is then communicated from the BSS 46 to a serving GPRS (general packet radio service) Support Node (SGSN) 48. Thereafter, a suspend request/response 50 is communicated between the SGSN 48 and MME 20 and an update of bearer(s) 52 takes place between the MME 20 and a serving gateway (S-GW) 54.
The UA 10 signals a paging response 56 to the BSS/RNS 46, which in turn forwards this paging response to the MSC 16. If the CS fallback entails a change of the MSC 16, additional steps may be carried out, as indicated in box 58, such as communicating a connection rejection 60 from the MSC 16 to the BSS!RNS 46, communicating a connection release 62 from the BSS/RNS 46 to the UA 10, and an LA update or combined RA/LA update 64. Finally, a CS call establishment procedure 66 occurs, such that, as indicated in FIG. 1, the UA 10 can move, as indicated by arrow 68, from communicating with the E-UTRAN cell 12 to communicate, as indicated by arrow 70, with the GERAN or UTRAN cell 14 over a CS channel,
When implementing CS fallback, delay may be a concern. If the UA 10 is initially camped on E-UTRAN cell 12 and wishes to access CS domain services in the GERAN or UTRAN Cell 14, a CS fallback process may be executed. While a radio resource control (RRC) connection setup procedure of the CS fallback process may be relatively short (e.g., about 150 ms is the target time for the E-UTRA system design), measurement steps and a step for selecting the target cell for CS domain services can potentially take a significant amount of time. As such, CS fallback may be delayed resulting in delays in establishing the CS domain services, possibly delaying the establishment of a connection for the user or negatively affecting other services accessed by the UA 10.
In addition to this potential for a user experiencing a perceivable delay in services, CS fallback can result in inefficient or inappropriate uses of network resources. For example, when a UA is paged in a GERAN or UTRAN network for a mobile-terminating call, some information is communicated by the network in the paging message. That is, the paging message may provide an indication of the service for which the UA is paged, or an indication of the appropriate radio channel type for supporting the service. Similarly, in case of a mobile-originating (MO) call, the UA is indicating to the network an establishment cause reflecting the service or the channel type requested. Thus, the network can reasonably allocate channels appropriate for the desired communication.
However, such information either is not available on the corresponding E-UTRAN interfaces used when initiating the CS fallback procedure, or is available but is not assessed for requesting/allocating the radio channels in GERAN, UTRAN or E-UTRAN. As a consequence, the network may decide to allocate non-optimal resources, such as a signaling channel for serving a voice call, which can affect the CS fallback performance, or a traffic channel for serving a signaling procedure, causing a waste of the radio resource.
Thus, systems and methods that address the above-listed issues and allow the setting and the usage of optimal resources for CS fallback would provide a useful improvement in the art.